dt-bindings: clock: exynos850: Add Exynos850 CMU_G3D

CMU_G3D generates Gondul GPU and bus clocks for BLK_G3D.
Add clock indices and binding documentation for CMU_G3D.

Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Sam Protsenko <semen.protsenko@linaro.org>
Link: https://lore.kernel.org/r/20230223042133.26551-2-semen.protsenko@linaro.org


Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>